The present invention relates to a mesoporous silica, a mesoporous silica composite material, and processes for producing such a silica and such a composite material. More particularly, the present invention relates to a mesoporous silica and a mesoporous silica composite material, both having superior alkaline resistance and being suitably used particularly as a separation membrane (e.g. a ceramic membrane) or a catalytic support for solid-liquid system, in which an alkaline liquid may be used; as well as to processes for producing such a silica and such a composite material.
In recent years, attention has been paid to mesoporous silica with a uniform mesopore structure, typified by MCM-41 (see JP-A-5-503499) and FSM-16 (see J. Am. Chem. Soc., 114, 10834, 1992). Mesoporous silica is synthesized using the micelle structure of a surfactant as a template; therefore, mesoporous silica has a structure in which pores with nano meter size in diameter are arranged periodically, and the size of the pore diameter is dependent upon the carbon chain length of the surfactant. Accordingly, mesoporous silica is characterized in that it has pores with uniform diameter and the diameter can be controlled appropriately. Owing to these characteristics, mesoporous silica is expected to be used as a separation membrane enabling a high selectivity and a catalytic support with high performance; and processes for synthesis of mesoporous silica have been proposed in, for example, Chem. Commun., 2147, 1998 and J. Memb. Sci., 182, 235, 2001.
In some fields using a separation membrane enabling a high selectivity and a catalytic support of high performance, for example, the medicinal field and the food field, alkaline reagents are used. With conventional separation membranes and catalytic supports, however, there have been cases that their washing with such an alkaline reagent is impossible or they have no sufficient durability to the alkaline reagent. Therefore, conventional separation membranes and catalytic supports have not been fully satisfactory in general applicability. No sufficient solution has yet been proposed to solve such a problem.